This invention relates to a cap for use on palletised loads, more particularly the type of cap having at least two strapping strands retractable into housings through openings at opposite sides (at least) of the cap, spring means within the housings for retracting the strapping strands, hooks on the free ends of the strapping strands for engagement with the underside of the platform of a pallet (e.g. a 2-way or 4-way pallet), tensioning means within the housings for tightening the strapping strands between the cap and the pallet after interposing a load between the cap and the pallet, and stop means for limiting retraction of the hooks into the housings when not engaged with a pallet.
Such a cap can be used without need to modify existing pallets, particularly—but not exclusively—those made of wood. The preferred form of hook has two prongs spaced apart so as to fit one to each side of a middle spacer of a pallet, without being in danger of damage or dislodgement by the forks of a fork-lift truck.
Two such caps are to be found in WO-A-01/96203.
In one of those caps each strapping strand is a wire or non-metallic rope retractably wound spirally on a ‘thin’ reel within the respective housing and having a short cylindrical core between annular flanges spaced apart by negligibly more than the overall diameter of the rope, so that the rope will be wound spirally on the core, the axis of the reel being perpendicular to the general plane of the cap, the core being on a shaft rotatably mounted within the housing, there also being provided a rewind spring coiled round the shaft alongside the reel, stop means limiting the extent to which the hook can be drawn into the housing by the action of the rewind spring, a ratchet concentric with the reel and rotatable with the reel and shaft, with a pawl for engaging teeth on the ratchet to stop or prevent pulling of the rope from the reel, and manually-operable means for tensioning the rope when the pawl has been engaged with a tooth on the ratchet, particularly characterised in that each tooth of the ratchet has a pawl-engageable face inclined forwardly from its radially inner end with respect to a radial line from the axis of the shaft through said radially inner end of said face and with respect to the direction of unwinding of the rope from the reel, the pawl has a complementary face for mutual engagement with said face of any one tooth of the ratchet, the pawl is provided with spring-loading means with manually-operable means for changing the effect of the spring loading over between urging the pawl into engagement with the ratchet and towards a position holding the pawl clear of the ratchet, and in that the manually-operable tensioning means is by way of a separate wrench engageable with one end of the shaft. While the reel can accommodate an adequate length of rope; and a separate wrench can have such a length of handle as to enable adequate tension to be applied to each wire or rope, application of the wrench to the cap when placed on a load of a height of, say, two metres is very difficult, even for a person of above average height. Likewise, access to the manually-operable change-over means for the ratchet is very difficult, especially as the change-over cannot be effected without use of the wrench for slight additional tensioning of the wire or rope to free the pawl from the ratchet.
In the other cap each strapping strand is a strap, there being within the respective housing parallel guides between ends of the housing, at one end of which is the opening; a crosshead slidable along the guides towards and away from the opening, the crosshead being mainly constituted by crossbars of graduated diameters; a fixed array of graduated crossbars adjacent the opposite end of the housing from the crosshead, the axes of the crossbars in the crosshead and the fixed array all being in a common plane with the smallest diameter crossbars being the nearest to each other, the strap having its inner end secured to one of the smallest diameter crossbars and being lapped in multi-purchase array round the other smallest diameter crossbar and each successively greater diameter crossbar in the crosshead and fixed array in turn, and with the final lap of the strap emerging from the opening in the housing, and spring means to urge the crosshead away from the fixed array; the total length of strap that can be accommodated being principally dependent on the number and lengths of laps between the crosshead and the fixed array, and the number of laps being determined by the number of crossbars in the crosshead and in the fixed array (e.g. three crossbars in one and two in the other giving five laps), the diameters of the crossbars can be but a few millimetres each consistent with being strong enough to carry the loads in the strap generated by the spring means, the tensioning means being a lever with an over-centre locking action rotating a slotted crossbar through which the strap passes. The length of strap that can be accommodated is very limited; and the length of the lever and the extent to which it can rotate the slotted crossbar are so limited that adequate tension in the straps is difficult to achieve, especially in view of elasticity/stretchability of the straps.